Candles have been known and used for illumination since early civilization. A typical candle is formed of a solid or semi-solid body of combustible waxy material and contains an combustible fibrous wick embedded within the waxy material. When the wick of a candle is lit, the generated heat melts the solid wax, and the resulting liquid flows up the wick by capillary action and is combusted. At present, although many advanced illuminating devices are available, candles are still popularly used for decoration or on a special situation as a holiday.
For a long time, beeswax was has been in common usage as a natural wax for candles. Over one hundred years ago, paraffin came into existence, in parallel with the development of the petroleum refining industry. Paraffin is produced from the residue leftover from refining gasoline and motor oils. Paraffin was introduced as a bountiful and low cost alternative to beeswax, which had become more and more costly and in more and more scarce supply.
Today, paraffin is the primary industrial wax used to produce candles. Conventional candles produced from a paraffin wax material typically emit a smoke and can produce a bad smell when burning. In addition, a small amount of particles (xe2x80x9cparticulatesxe2x80x9d) can be produced when the candle burns. These particles may affect the health of a human when breathed in.
Accordingly, it would be advantageous to have other materials which can be used to form clean burning base wax for forming candles. If possible, such materials would preferably be biodegradable and be derived from renewable raw materials. The candle base waxes should preferably have physical characteristics, e.g., in terms of melting point, hardness and/or malleability, that permit the material to be readily formed into candles having a pleasing appearance and/or feel to the touch, as well as having desirable olfactory properties.
In the past, attempts to formulate candle waxes from vegetable oil-based materials have often suffered from a variety of problems. For example, relative to paraffin-based candles, vegetable oil-based candles have been reported to exhibit one or more disadvantages such as cracking, air pocket formation, product shrinkage and a natural product odor associated with soybean materials. Various soybean-based waxes have also been reported to suffer performance problems relating to optimum flame size, effective wax and wick performance matching for an even burn, maximum burning time, product color integration and/or product shelf life. In order to achieve the aesthetic and functional product surface and quality sought by consumers of candles, it would be advantageous to develop new vegetable oil-based waxes that overcome as many of these deficiencies as possible.
The present invention relates to candles having low paraffin content and methods of producing such candles. The candles are typically formed from a tricylglycerol-based wax, such as vegetable oil-based wax, a biodegradable material produced from renewable resources. Since the candles are formed from a material with a low paraffin content and preferably are substantially devoid of paraffin, the candles are generally clean burning, emitting very little soot. The combination of low soot emission, biodegradability and production from renewable raw material makes the present candle a particularly environmentally friendly product.
The present wax may be useful in forming pillar and votive candles. The wax is desirably formulated to inhibit surface adhesion to facilitate release of a candle from its mold in the production of pillar and/or votive candles. Good mold release is an important economic consideration in the manufacture of candles, allowing rapid production. In addition, it is desirable that the wax is capable of being blended with natural color additives to provide an even solid color distribution.
The triacylglycerol-based wax which may be used to form the present candles is typically solid, firm but not brittle, generally somewhat malleable, with no free oil visible. The wax includes a triacylglycerol component and a polyol fatty acid partial ester component and generally has a melting point of about 130 to 145xc2x0 F. (circa 54 to 63xc2x0 C.). The wax is commonly predominantly made up of a mixture of the triacylglycerol component and the polyol fatty acid partial ester component, e.g., the wax commonly includes at least about 70 wt. % of the triacylglycerol component and about 3 to 30 wt. % of the polyol partial ester component. Desirably, the triacylglycerol-based wax has an Iodine Value of about 20 to 40. The triacylglycerol component generally has a fatty acid composition which includes about 50 to 70 wt. % saturated fatty acids and about 30 to 45 wt. % 18:1 fatty acids.
In general, oils extracted from any given plant or animal source comprise a mixture of triacylglycerols characteristic of the specific source. The mixture of fatty acids isolated from complete hydrolysis of the triacylglycerols and/or other fatty acid esters in a specific sample are referred herein to as the xe2x80x9cfatty acid compositionxe2x80x9d of that sample. By the term xe2x80x9cfatty acid compositionxe2x80x9d reference is made to the identifiable fatty acid residues in the various esters. The distribution of fatty acids in a particular oil or mixture of esters may be readily determined by methods known to those skilled in the art, e.g., via gas chromatography or conversion to a mixture of fatty acid methyl esters followed by analysis by gas chromatography.
The polyol fatty acid partial ester component can be derived from partial saponification of a vegetable-oil based material and consequently may include a mixture of two or more fatty acids. For example, the polyol fatty acid partial ester component may suitably include polyol partial esters palmitic acid and/or stearic acid, e.g., where at least about 90 wt. % of the fatty acid which is esterified with the polyol is palmitic acid, stearic acid or a mixture thereof. Examples of suitable polyol partial esters include fatty acid partial esters of glycerol and/or sorbitan, e.g., glycerol and/or sorbitan monoesters of mixtures of fatty acids having 14 to 24 carbon atoms. More desirably, at least about 90 wt. % of the fatty acyl groups in the polyol partial esters have 16 or 18 carbon atoms. As employed herein, the term xe2x80x9cfatty acyl groupxe2x80x9d refers to an acyl group (xe2x80x9cxe2x80x94C(O)Rxe2x80x9d) which includes an aliphatic chain (linear or branched).
The triacylglycerol component may suitably be chosen to have a melting point of about 54xc2x0 C. to 63xc2x0 C. (circa 130xc2x0 F. to 145xc2x0 F.). One embodiment of such a triacylglycerol stock can be formed by blending fully hydrogenated and partially hydrogenated vegetable oils to produce a blend with an Iodine Value of about 25-45 and the desired melting point. For example, a suitable triacylglycerol stock can be formed by blending appropriate amounts of fully hydrogenated soybean and/or palm oils with a partially hydrogenated soybean oil having an Iodine Value of about 60 to 75. As used herein, a xe2x80x9cfully hydrogenatedxe2x80x9d vegetable oil refers to a vegetable oil which has been hydrogenated to an Iodine Value of no more than about 5. The term xe2x80x9chydrogenatedxe2x80x9d is used herein to refer to fatty acid ester-based stocks that are either partially or fully hydrogenated. Instead of employing a highly hydrogenated vegetable oil, a highly unsaturated triacylglycerol material derived from precipitating a hard fat fraction from a vegetable oil may be employed. Hard fat fractions obtained in this manner are predominantly composed of saturated triacylglycerols.
It is generally advantageous to minimize the amount of free fatty acid(s) in the triacylglycerol-based wax. Since carboxylic acids are commonly somewhat corrosive, the presence of fatty acid(s) in a triacylglycerol-based wax can increase its irritancy to skin. The present triacylglycerol-based wax generally has free fatty acid content (xe2x80x9cFFAxe2x80x9d) of no more than about 1.0 wt. % and, preferably no more than about 0.5 wt. %.
It has been reported that a candle with a string-less wick can be formed by suspending fine granular or powdered material, such as silica gel flour or wheat fiber in a vegetable oil such as soybean oil, cottonseed oil and/or palm oil. The inclusion of particulate material in a candle wax can result in a two phase material and alter the visual appearance of a candle. Accordingly, the present triacylglycerol-based wax is preferably substantially free (e.g., includes no more than about 0.5 wt. %) of particulate material. As used herein, the term xe2x80x9cparticulate materialxe2x80x9d refers to any material that will not dissolve in the triacylglycerol component of the wax, when the wax is in a molten state.
The triacylglycxerol-based wax may also include minor amounts of other additives to modify the properties of the waxy material. Examples of types of additives which may commonly be incorporated into the present candles include colorants, fragrances (e.g., fragrance oils), insect repellants and migration inhibitors.
If the present wax is used to produce a candle, the same standard wicks that are employed with other waxes (e.g., paraffin and/or beeswax) can be utilized. In order to fully benefit from the environmentally-safe aspect of the present wax, it is desirable to use a wick which does not have a metal core, such as a lead or zinc core. One example of a suitable wick material is a braided cotton wick.
The present candles may be formed by a method which includes heating the triacylglycerol-based wax to a molten state and introduction of the molten triacylglycerol-based wax into a mold which includes a wick disposed therein. The molten triacylglycerol-based wax is cooled in the mold to solidify the wax and the solidified wax is removed from the mold. This is facilitated by the use of a wax, such as the present triacylglycerol-based wax, which does not adhere to the sides of the mold.